Problem with simpleFoam
 

Hi
When I run my case with simpleFoam with a refine mesh, after some iteration I have this error message why? (my k and epsilon aren't zero)

time step continuity errors : sum local = 2.25645e+45, global = -2.2833e+38, cumulative = -2.2833e+38
#0 Foam::error:printStack(Foam::Ostream&) in "/user/parolini/OpenFOAM/OpenFOAM-1.7.x/lib/linux64GccDPOpt/libOpenFOAM.so"
#1 Foam::sigFpe::sigFpeHandler(int) in "/user/OpenFOAM/OpenFOAM-1.7.x/lib/linux64GccDPOpt/libOpenFOAM.so"
#2 __restore_rt at sigaction.c:0
#3 Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/user/OpenFOAM/OpenFOAM-1.7.x/lib/linux64GccDPOpt/libOpenFOAM.so"
#4 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/user/OpenFOAM/OpenFOAM-1.7.x/lib/linux64GccDPOpt/libfiniteVolume.so"
#5 Foam::lduMatrix::solverPerformance Foam::solve<double>(Foam::tmp<Foam::fvMatrix<doubl e> > const&) in "/user/OpenFOAM/OpenFOAM-1.7.x/lib/linux64GccDPOpt/libinc$
#6 Foam::incompressible::RASModels::kEpsilon::correct () in "/user/OpenFOAM/OpenFOAM-1.7.x/lib/linux64GccDPOpt/libincompressibleRASModels.so"
#7 main in "/user/OpenFOAM/OpenFOAM-1.7.x/applications/bin/linux64GccDPOpt/simpleFoam"
#8 __libc_start_main in "/lib64/libc.so.6"
#9 Foam::regIOobject::writeObject(Foam::IOstream::str eamFormat, Foam::IOstream::versionNumber, Foam::IOstream::compressionType) const in "/user/OpenFOAM/OpenFOAM$

hi daniele,

time step continuity errors : sum local = 2.25645e+45

this seems to produce a floating point exception caused by too large numbers.

maybe check the velocity field of the last time step before divergence?
could be that a bc is not set correctly.

best,
moritz

Hi
Time step error explode when I refine mesh, i don't understand...
this is my case, is a atmospeheric bundary layer with a obstacle on the bottom

have you tried to change the relaxation factors for p and U?
and maybe initialize with some magnitude!

Initialize p and U in 0 dir?. U is initialized but p is set equal zero, I try to change it . How can change relaxation factor?

Thank you

no, initializing U is enough ;). the relaxation factors are set in system/fvSolution like that:

relaxationFactors
{
U 0.3;
p 0.7;
}

they sould be 1 in sum. for the beginning 0.3 for U may be better, you might change it to 0.7 and p to 0.3 after a while.

And factors for k epsilon? 0,8 is good? What value can i use to initialize U?

Thanks

you can try to switch off turbulence in constant/RASProperties and calculate some laminar iterations. then you can start from there with turbulence switched on. i don't know which factors for k and eps to use, depends on your case, but you can start with 0.8 and decrease them if its diverging.

With the factor that you give me time step continuity error is ok! Thanks! You are very kind. My result now are better. Can I ask you another thing? This is my wall shear stress on bottom The obstacle has a step with a ricircularion bubble; and in my plot I have a overshooting. How can i try to eliminate it?

sorry i have no experience with that yet... maybe someone else :).